1. Field of the Invention.
This invention relates to a circuit for converting digital signals to analog signals. More particularly, this invention relates to a digital-to-analog converter having an interpolator circuit, and a noise shaping circuit and a semi-digital filter.
2. Brief Description of the Related Technology
Converting digital signals to analog signals is accomplished using a digital-to-analog converter (DAC). These DACs typically operate by a resistor, capacitor divider, or current steering method to convert digital-to-analog signals or, operate using a sigma-delta conversion method. Sigma-delta DACs are often preferred because of their inherent feasibility to be manufactured as integrated circuits in standard digital integrated circuit processes.
Many DACs utilize oversampled digital data output from an interpolation circuit, which is then converted by DAC circuitry into an analog output. Sigma-delta DACs inherently introduce noise outside the passband of the DAC converter circuit. To alleviate this out of band noise, various filtering techniques are employed.